It is a matter of no little pride for the libel reform campaign that the first bill to be published under the new coalition government is aimed at reforming the UK's hideous defamation laws. An issue that was regarded with hostility or disdain at Westminster has forced its way up the political agenda.

Lord Lester's private member's bill represents the first concerted attempt to codify the balance between free expression and the right to reputation. It seeks to introduce a statutory defence of responsible publication on a matter of public interest; clarify the defences of justification and fair comment; require claimants to show substantial harm, and corporate bodies to show financial loss; encourage quick and cost-effective settlement of disputes through arbitration without recourse to costly litigation. And, in a nod to the 21st century, it addresses the problems of the internet age, including multiple publications and the responsibility of internet service providers and hosts.

Lester's defamation bill constitutes a quiet revolution. It sets out, as he puts it: "To reduce the chilling effect on freedom of expression and recourse to self-censorship that results from the vagueness and uncertainty of the present law. It also aims to encourage the free exchange of ideas and information, whilst providing an effective and proportionate remedy to anyone whose reputation is unfairly damaged."

Some free expression campaigners may argue that the bill does not go far enough. It does not, for example, address the burden of proof. But ours is not to cavil: it marks a major step forward, and should be supported as it moves through its legislative stages. The bigger danger is that it is destroyed or watered down beyond recognition, as the government caves in under pressure from those in the legal profession who have made tidy profits from an archaic and unbalanced body of law.

The claimant cabal has already begun to fight back. Addressing a meeting in the Inner Temple a few days before publishing his bill, Lester sought to fend off characteristically smug scoffing from several barristers. They seemed convinced that his bill was an attempt by reformers to ingratiate themselves with newspapers. They deliberately misrepresent the campaign for libel reform as representing media organisations. We do not. We aim to repair a body of law that has seen scientists, doctors, NGOs, bloggers and others forced into apologising for and retracting comments, articles and books, even though they have done nothing wrong. We aim to make it harder for oligarchs and sheikhs to use English courts to stifle free speech around the world.

Opponents of libel reform know they are operating in a changed environment. Since Index on Censorship launched the libel reform campaign last November, in conjunction with English Pen and Sense About Science, we have amassed a groundswell of popular support. More than 50,000 people have signed our petition and public figures have spoken out.

Only recently, however, have politicians begun to appreciate the clamour. The working group, established by Jack Straw when he was justice secretary, was an important first step. Somewhat hurriedly he tried to push through in the dying days of the last parliament new rules that would have slashed success fees for libel lawyers from 100% to 10%. The issue of costs must be tackled again.

Gratifyingly, all three main parties went into the election with manifesto commitments to reform the law. The Liberal Democrats have been the most consistent advocates, and with Nick Clegg firmly ensconced as deputy prime minister and leading on the government's plans for constitutional reform and civil liberties, the issue is in good hands. The Ministry of Justice is keen on supporting him, but early signals from Ken Clarke, its secretary of state, do not appear to be encouraging. Hopes may fall on his Lib Dem number two, Lord McNally.

All but the most recalcitrant accept that the law needs modernising. It relies on bizarre precedent, such as the Duke of Brunswick sending his manservant to Paris to gather a copy of the Weekly Dispatch which had offended him. But there is a bigger problem. Many lawyers appear perturbed by the idea of free speech. They are comfortable in a situation in which they, and not an elected parliament, rule what information the public has a right to know. They, and they alone, have a vested interest in maintaining the status quo.